Statutory Defenses to Proposition 65 Claims

Reviewed by Jason Foscolo, Food & Beverage Attorney — Founder, Foscolo & Diefenbach PLLC (The Food Law Firm). Former USMC JAG; LL.M. in Agricultural & Food Law (University of Arkansas).
Reviewed by a licensed attorney. Last reviewed: June 2026.

This article is general information about California Proposition 65, not legal advice, and does not create an attorney–client relationship. Consult qualified counsel about your specific facts.

Statutory defenses to Prop 65 claims give food manufacturers specific legal grounds to challenge liability when facing enforcement under California’s Proposition 65. These defenses include arguments that the product does not exceed regulatory thresholds, that the business qualifies for a small-entity exemption, or that the chemical exposure is naturally occurring. Each defense carries its own evidentiary burden, regulatory citation, and cost-benefit profile. Understanding how and when to assert these statutory defenses is critical for manufacturers seeking to minimize legal exposure and preserve market access in California.

If you have received a 60-day notice about a Prop 65 violation, read this first: Use the Attorney-Client Privilege to Prepare for Litigation. Every valid defense starts with controlled analysis protected under privilege.

• Establish that the product does not violate the statute. The most direct statutory defense is scientific. If the product or batch does not contain the listed chemical at levels exceeding the established No Significant Risk Level (NSRL) or Maximum Allowable Dose Level (MADL), then no Prop 65 warning is required. Manufacturers must conduct accredited, validated laboratory testing to establish chemical content and exposure levels. Retain counsel before testing so that findings remain confidential and disclosure only ever supports the defense.
• The Small Business Exemption. The law exempts businesses with nine or fewer employees from Prop 65’s warning requirements. This exemption applies regardless of product content or exposure. However, manufacturers should not rely on it without legal guidance: certain retailers, copackers, or upstream suppliers may still bear compliance obligations even when the manufacturer itself qualifies. (See Cal. Health & Safety Code § 25249.11(b): “‘Person in the course of doing business’ does not include any person employing fewer than 10 employees…”)
• Naturally Occurring Chemical Exemption. Some chemicals, particularly heavy metals like arsenic, cadmium, and lead, appear in food due to natural uptake from soil or water. The naturally-occurring exemption may apply if the manufacturer can prove that no human activity introduced or increased the chemical content beyond unavoidable levels. To support this defense, the manufacturer must document supply-chain controls, environmental testing, and standard industry practices. This defense often requires expert reports, which must be commissioned through legal counsel to remain protected. (See 27 CCR § 25501(a) — a chemical in food is “naturally occurring” if it is a natural constituent of the food and has not been increased by human activity, or cannot be reduced below naturally occurring levels by good agricultural or manufacturing practices.)

Establishing that the product does not violate the statute. Proposition 65 plaintiffs’ attorneys are very forthcoming with the laboratory reports that support their claim; they often voluntarily turn over lab reports and the lot/batch numbers of the products tested. It is always wise to verify the result with an independent analysis. But if the manufacturer’s retained sample from the same batch yields a conflicting result, that alone does not resolve the matter. Two opposing lab results create a triable issue of fact, and plaintiffs’ firms use that uncertainty to maintain settlement leverage and build a credible path toward expensive litigation. Defending the product’s compliance through scientific testing may look straightforward, but asserting this defense in full requires litigation. If the expected cost of trial exceeds the product’s settlement value, a strategic settlement often serves the manufacturer better than a symbolic legal stand.

The Small Business Exemption. Believe it or not, this is the most limited defense available. The legal definition of “employee” includes part-time and temporary workers, so a manufacturer that employs ten individuals—each for a single shift—may still cross the threshold. Even when the exemption clearly applies to the manufacturer, it does not shield downstream entities: a California retailer with more than ten employees remains subject to Prop 65 and will, in turn, demand indemnification from its supplier regardless of the supplier’s exemption status. Asserting this defense may avoid direct liability, but it rarely avoids pressure or cost.

The Naturally Occurring Exemption. The naturally-occurring chemical exemption under 27 CCR § 25501(a) imposes an enormous evidentiary burden. To assert it, the manufacturer must prove that no human activity contributed to the presence of the listed chemical—a standard that requires expert testimony covering every stage of production, from cultivation to final packaging. Soil composition, equipment and processing practices, and packaging materials must all be examined to confirm no transfer occurred during manufacture or shipment, and the resulting expert reports must survive scrutiny from plaintiffs experienced in discrediting marginal scientific defenses. These costs can be justified only when sales volume or long-term reputational risk warrants a protracted strategy. The defense may lower the settlement value of a case, but only when the investment in expert analysis has enough downstream impact to tip the scales.

This page’s most likely reader is another attorney or an in-house lawyer doing deep due diligence. We accept Prop 65 matters and referrals from other counsel. If you are evaluating a defense and want a second set of experienced eyes on the threshold-testing or naturally-occurring analysis, review our litigation services and contact us.

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Jason Foscolo Founder of The Food Law Firm — fractional general counsel for food & beverage businesses nationwide.

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